Hydrochloric acid is produced commercially by burning hydrogen and chlorine to form hydrogen chloride gas, which is then dissolved in water to form the desired hydrochloric acid. Typically the hydrogen and chlorine are introduced into a vertical graphite chamber approximately 25 to 40 feet high with an inside diameter of about 33 inches, through a burner cap. The conventional burner cap resembles a short piece of pipe with one end closed or capped and separate hydrogen and chlorine orifices in the sides of the cap through which the gases exit separately to mix and burn at the outside surface of the burner cap. The graphite chamber serves as a holder for the flame and also cools the product hydrogen chlorine gas with a film of water flowing down the outside of the chamber. The discharge through the side walls of the conventional burner cap is essentially radial so that a bowl shaped flame is generated by the combustion. The flow rate of the gases fed to the burner cap must be controlled so that the flame generated does not impinge on the interior walls of the graphite combustion chamber. Flame contact with the graphite walls, which are relatively expensive, would result in their rapid destruction. The necessity to avoid such flame contact restricts the capacity of the burner assembly accordingly.